How can I sort items in a list view?

When you're in a list, you can change the sorting by taping the menu in the top left corner, the second menu item is for sorting:

You can chose between sort by:

Alphabetical

Time

Frequency

The arrows on the right will let you toggle different variations (A-Z vs Z-A, for example). Sorting by frequency mostly means by frequency of interaction, i.e. how often you interacted with that person, for example.